1216334
Description
Flashcards by future_med_student, updated more than 1 year ago
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Created by future_med_student
almost 12 years ago
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| Question | Answer |
| What are isomers? | Isomers are compounds that have the same molecular formula, but different structural formula. |
| What are stereoisomers? and name the two types. | Stereoisomers have the same molecular formula, but their atoms are arranged differently in space. The two types are optical isomers and E/Z isomers |
| Under what conditions does E/Z isomerism occur? | It only occurs when there are Carbon-Carbon double bonds (alkenes) that have no rotation, and when two different groups are attached to each Carbon atom. |
| State what the structure looks like for E and Z isomerism. | When it is E isomerism, the same/similar compounds will be diagonal to each other. In Z isomerism, the same/similar compounds are on the same side of the structure. |
| What is the alternate name for E/Z isomerism? Why does this form not always work? | E/Z isomerism can also be called cis-trans isomerism. Cis is when the similar groups are on the same side, and Trans is when they are diagonal. This form doesn't work when all groups attached to the carbon atoms are different. |
| How does the E/Z naming work when not all groups attached to the Carbon atoms are the same? | The higher priority groups are taken into consideration. If the higher priority group on each carbon is diagonal, then it is E. If the higher priority group on each carbon is on the same side, then it is Z. |
| What are optical isomers? | Optical isomers are mirror images of each other. They have a chiral carbon atom. (An atom that has four different groups attached to it) They are also non-superimposable. |
| What is a chiral carbon? | A carbon atom that has 4 different groups attached to it. The four different groups can be re-arranged to form two different molecules. These two different molecules are called enantiomers or optical isomers. |
| Why are optical isomers said to be 'optically active'? | Optical isomers rotate in plane polarised light. One optical isomer rotates clockwise while the other rotates anti-clockwise. |
| What is plane polarised light? | Plane polarised light is light that vibrates in one direction alone, unlike normal like that vibrates in all directions. |
| What is a racemic mixture? | A racemic mixture contains equal quantities of both optical isomers of an optically active compound |
| Why do racemic mixtures not show an optical activity? | This is because in racemic mixtures the two optical isomers cancel out each other's light rotating effect. |
| What two compounds can be reacted together to give a racemic micture? | Two achiral compounds can be reacted together to give a racemic mixture of a chiral product. |
| How can optical activity be used to determine a reaction mechanism? | If you begin with a single optical isomer reactant and the product is a racemic mixture of two optical isomers it's an Sn1 reaction. If you begin with a single optical isomer reactant and a single optical isomer product, it's an Sn2 reaction. |
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